Japanese Unexamined Patent Application Publication No. 2014-107499 (Patent Literature 1) discloses a technology in which a JTE region is formed on a sidewall surface of the mesa structure.
Japanese Unexamined Patent Application Publication No. 2008-211171 (Patent Literature 2) discloses a technology in which an electric field relaxation structure is formed on a part of a sidewall surface of the mesa structure.